Jamal Imani; Ataollah Ebrahimi; Bahram Gholinejad; Pejman Tahmasebi
Volume 28, Issue 4 , November 2021, , Pages 640-651
Abstract
In the present study, we compared different sampling patterns and different plot dimensions to estimate the percentage of canopy cover and forage production in rangeland habitats around Choghakhor Wetland. The choice of sampling method was based on the opinion of the researcher. ...
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In the present study, we compared different sampling patterns and different plot dimensions to estimate the percentage of canopy cover and forage production in rangeland habitats around Choghakhor Wetland. The choice of sampling method was based on the opinion of the researcher. Sampling was performed in three different plant communities, in two patterns of six and three plots. Different dimensions of the plot (including 1×1, 1×2, 2×2, and 3×3 m2) were used as a nest to estimate the production and the percentage of canopy cover. Sampling was in each community within 30 sampling units along three transects. The canopy cover of the species was estimated by estimating and producing them by double sampling. Species density was calculated by counting bases in 2×2 plots. In each population, the type of distribution of dominant species was determined by statistical tests. The results showed that two different sampling patterns and four different plot dimensions have significant differences in estimating the percentage of cover and plant production (P≤0.01). According to the interaction of the community and the pattern, plot dimensions with pattern and plant community, patterns and plot dimensions with each other, there was no significant difference. The effect of plant community with plot dimensions on a cover percentage at (p≤0.05) and production at (p≤0.01) is significant. In Gundellia tournefortii-Couisinia Bakhtiari plant community with random distribution patterns, two different sampling patterns in 1×1 and 1×2 m2 plots were significantly different, and in other dimensions, no significant difference was observed. The two different sampling patterns in the Daphnea mucronata-Astragalus adsendence community with the uniform dispersion pattern were significantly different only in plot 1×1 (p≤0.05) and شdid not differ in other sizes. The mentioned patterns in the population of Melica persica-Agropyron trichophorum with the heap pattern distribution in statistical plots of 3×3 m2 did not show a statistical difference, but in other dimensions showed a significant difference (p≤0.05).
Jamal Imani; Ataollah Ebrahimi; Bahram Gholinejad; Pejman Tahmasebi
Volume 28, Issue 3 , October 2021, , Pages 450-471
Abstract
The present study was conducted to investigate the differences between several remote sensing indices, four different plot sizes and two different sampling methods to estimate the percentage of plant cover and production in three plant communities in 2013. Ground sampling was performed in three communities ...
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The present study was conducted to investigate the differences between several remote sensing indices, four different plot sizes and two different sampling methods to estimate the percentage of plant cover and production in three plant communities in 2013. Ground sampling was performed in three communities with different dominant vegetation in two forms of six and three quadrats. Four different dimensions of the quadrats were used nested to estimate production and coverage percentage. Sampling was performed in each community within 30 pixels along three transects with different heights (sampling method and testing were performed according to the researcher opinion). Dominant plant density was measured by counting the bases per plot, plant cover percentage as an estimate and production in the form of double sampling in relation to cover percentage. The results showed that with increasing plot area, the degree of correlation of plant indexes of Landsat image and their significance in relation to production and percentage of plant cover will increase. But this increase in community 2 is more dramatic in most respects with predominantly shrubs. As in this community, most of the studied indicators in 3 × 3 plot have a correlation and a reliable model, and in the three sizes of 1×1, 2×1 and 2×2 plots, the resulting models are not valid enough and have high RMSE. In community one with dominant broadleaf plants, only the model obtained in 1×1 plot and in community two with dominant plants, the model obtained in 1×1 and 1×2 plots are not statistically valid, although sometimes they have a significant correlation. The results of two different models are statistically different in communites 1 and 3 and there was no significant difference between them in community 2. According to the results of the study of indicators in terms of correlation and model validity, the two indicators NDVI and CTVI can be used in community 1, NDVI and TSAVI1 in community 2 and NDVI, NRVI and TSAVI1 in community 3 recommended for estimating production and percentage of plant cover using satellite images.
Jamal Imani; Ataollah Ebrahimi; Bahram Gholonejad; Pezhman Tahmasebi
Volume 25, Issue 1 , April 2018, , Pages 152-169
Abstract
Identifying and evaluating rangeland ecosystems is the first step in managing these resources. Without knowledge of rangeland condition, no management plan can be developed for it. For this purpose, three sites with different dominant species were selected for sampling. In each site, ...
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Identifying and evaluating rangeland ecosystems is the first step in managing these resources. Without knowledge of rangeland condition, no management plan can be developed for it. For this purpose, three sites with different dominant species were selected for sampling. In each site, 30 sampling units of 900 m2 were determined along three transects and sampling quadrates were established in these units. After correction and processing, the NDVI and SAVI indices were extracted from Landsat 8 images, and their correlation with vegetation cover percentage and production was calculated. The results showed that the correlation of indices with the vegetation cover percentage and production was significant in each of the three sites. In each site, the NDVI had the most correlation with dominant vegetation form, while SAVI reduced the effect of soil and was more related with low vegetation cover species. This is related to the SAVI equation and this index could reduce the effect of soil. The broadleaf species had the highest correlation with the NDVI index due to the plant structure and more reflection.
Jamal Imani; Ataollah Ebrahimi; Pejman tahmasebi; Bahram Gholinejad
Volume 24, Issue 2 , July 2017, , Pages 429-440
Abstract
The use of satellite data is one of the proper methods, which makes studying ecosystems less costly. This research was carried out to determine the correlation among the vegetation cover of dominant species in three sites with the NDVI index. For this purpose, a study was conducted on three different ...
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The use of satellite data is one of the proper methods, which makes studying ecosystems less costly. This research was carried out to determine the correlation among the vegetation cover of dominant species in three sites with the NDVI index. For this purpose, a study was conducted on three different vegetation types. In each region, a range was determined for sampling. Then, within this range and in the horizontal direction, 30 sampling units of 30 x 30 m were selected along three 900-meter transects in a random-systematic manner. In each sampling unit, nested quadrates with dimensions of 1 × 1, 2 × 2 m were placed. In order to prevent geometric errors, the 900-meter ranges were 60 meters apart. Within each sampling unit, geographic coordinates were recorded with GPS. The number of individuals and canopy cover percentage of dominant species were recorded separately in the plots. Then, the correlation of canopy cover percentage with NDVI index was obtained by processing Landsat 8 images. The distribution pattern was also determined using species density data. The results showed that in all species, the correlation coefficient of NDVI index was higher in the plots with higher area. Also, the correlation coefficient with one quadrat increased towards five quadrats. Due to the lack of high correlation between the total canopy cover percentage of a quadrat and the NDVI index, the use of one quadrat inside the pixel is not recommended in any way. Selecting the type of sampling depends on distribution pattern and species size as well as access to facilities and correlation coefficient acceptability. For species with clumped distribution, more quadrats are needed with proper distribution inside the pixel on the ground, so that sampling could be a good representation of the total pixel. In uniform distribution, fewer samples are needed since the whole pixel is the same in terms of plant growth.
Jamal Imani; Ali Tavili; Esaa Bandak; Bahram Gholinejad
Volume 17, Issue 3 , October 2010, , Pages 393-401
Abstract
Analysis of vegetation is one of the important factors in appropriate management of rangelands. The current research was conducted to evaluate canopy cover percentage, forage production, and species density in four areas including reference area, personal rangeland, key area and critical area in the ...
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Analysis of vegetation is one of the important factors in appropriate management of rangelands. The current research was conducted to evaluate canopy cover percentage, forage production, and species density in four areas including reference area, personal rangeland, key area and critical area in the region of village. In each area, 5 transects were established on which 10 quadrate 1 m were used with regard to the plant type and distribution of species. The lengths of each transect and the distance between them were determined 100 m and 20 m respectively according to the species density and distribution. Canopy cover percentage, forage production and species density were recorded in all quadrates. Clipping and weighing method was used to estimate forage production. Data analysis was performed using one way ANOVA and Duncan test. Results indicated that there was significant difference in canopy cover percentage (p≤ 0/1), forage production (p≤ 0/05) and species density (p≤ 0/01) among 4 studied areas. The result showed that with moving from reference to critical area, canopy cover percentage, forage production and species density dramatically decreased as palatable species (class I), average palatable species and non palatable and invasive species had the most canopy cover percentage, forage production and density respectively in reference area, personal rangeland and common area between village and critical area. Perennials and palatable grasses such as Bromus tomentellus and Hordeum bolbosum had the highest canopy cover percentage, forage production and density in reference area. With a gradual increase in grazing intensity, percentage of palatable species decreased while non palatable species like Boisseria squarrosa and Centaurea virgata increased. This research revealed that heavy grazing jeopardized the sustainability of the rangeland ecosystem by creating unfavorable changes in vegetation characteristics.
Jamal Emani; Ali Tavili; Essa Bandak; Mohammad Khosravi
Volume 17, Issue 2 , September 2010, , Pages 234-242
Abstract
Flood water spreading projections have been done with many objectives. One of these objectives is increasing vegetation cover. Flood water spreading leads to the increasing of soil moisture and as a result increasing forage production. In this study the effects of flood spreading are evaluated. This ...
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Flood water spreading projections have been done with many objectives. One of these objectives is increasing vegetation cover. Flood water spreading leads to the increasing of soil moisture and as a result increasing forage production. In this study the effects of flood spreading are evaluated. This assessment is done in aquifer of Mayhem district of Ghorveh state. In each rainfall that results into flood, 6 areas are flooded and 2 areas are not flooded. Therefore, 6 areas considered as the flood water spreading and 2 areas considered as the control site. The samplings of vegetation properties were performed in these eight areas. For this purpose, in each district, 5 transects each with a length of 100 m with 10 m interval from each other were situated and along each transect, 10 quadrates with an area of 1m were established. In each area, the characteristics of canopy cover percentage, forage production and species density were recorded. Analysis of data was performed using of un-paired T-test. Obtained results from T-test indicated that there is significant difference between canopy cover percentage (p≤ 0/1) and forage production (p≤ 0/05) while no significant difference was observed for species density in flooded and non-flooded areas. The results showed that the canopy cover increased from 41/91 percent in the control site to 62/18 percent in the flood spreading area. The forage production increased from 467/17 kg/ha in the control site to 632/17 kg/ha in the flood spreading area. Also the species density increased from 1/18 in the control site to 1/59 in the flood spreading area. Some of the plant species that are in the III classes from palatability aspect, decreased in the flood spreading area rather than control site.